engine overheating

engine overheating

So here in portland for the last week it has been 75-90 oddly. This is the first hot spell since i bought my truck. I had my worst overheating yesterday when it was ~88 degrees. A bit of history, my needle seems to behave as expected usually. It is to the left of C when i first start it, and slowly warms to the "o" or "r" of the word normal. Occasionally it jumps to the "m" or "a" fairly quickly, which has made me think i have a intermittent thermo. However, yesterday it went all the way to "a", "l", and to the H. During the overheating it was also idling poorly and struggled to accelerate when i first gassed it from a stop. I temped it and the upper hose was reading 190-ish and the metal thermo housing was ~207. when i turned the engine off finally it climbed to 212. This seems wayyy to hot and suggests the gauge was reading accurately. I did some reading on FTE and it seems like there might be air in the system. Was curious if others had ideas/thoughts? I found a receipt from the 90s when a PO "rodded out" the radiator - so it seems unlikely that the radiator is the problem. Also, what is the normal operating temp for a 351M? is it truly the thermo rating aka 195?

Re: engine overheating

I'll also add that it was starting to get warmer than usual today on a short drive, so this is looking to be typical behavior in warm weather until i address it. This is a trailer special, so this truck should not be overheating unless I'm pulling a 5,000 pound trailer uphill in the rocky mountains.

Re: engine overheating

195*F is a proper thermostat for a stock engine, and normal operating temperature.
Even 212*F is not way hot. The purpose of a pressure cap is to keep coolant from boiling above this temperature.

A radiator that is 25 years old and may have questionable/no maintenance or hard water in it is suspect.
Have you used the IR thermometer on the radiator outlet, or the water pump inlet?
How much heat is the radiator shedding? ie the Delta across it?
Does the radiator have a proper fan shroud?

Keep in mind that the 351C-M and 400 have a special thermostat that blocks the bypass when open.
Though more common thermostats will fit, they will not function correctly and the rear cylinder can overheat because of this.
DAMHIK....

So, if you're thinking of changing it please be sure to use the correct one.
Gary has the parts # listed here somewhere.

Re: engine overheating

Administrator

I agree with all that's been said. And Jim is spot-on, the Clevelands and M-blocks take a different thermostat, as explained here (Engines/351M & 400) on the Thermostats tab. Since very few people know that, I'd be willing to bet you have the wrong one in there.

But, I doubt that explains the overheating indications. Were it not for the poor running I'd say you have a gauge/sender problem rather than true overheating. And there might be other explanations for the poor running.

So check out the things the others said, make sure you have the proper thermostat, and check your initial timing as too late of timing can cause the engine to run warm.

Re: engine overheating

All spot on replies so far.
I know it is not something you would want to do when it is hot out, turn off the AC if it has it and turn heat on hot and fan on full speed.
Does the temp come down? Could point to a bad radiator.

The other thing is mud in the bottom of the cooling passages in the block.
No matter how much you try and flush it it is so fine and packed in the only way for it to be removed it is to hot tank the block.
Had a buddy that had a motor run hot, cooling system new had the block hot tanked and all was good.

I also have a motor that ran hot, car is a project now because of this, that the cooling system was mud when I go it. Flushing, 2 new radiators, new water pump, hoses, heater core even a fan shroud and the car never came with one from the factory (it did help a little).

I could never drive it far before it would over heat, you could hear the water boiling in the block!
The freeze plugs started to rust out of the motor, even 1 in the head! Each one I pulled I would take something (coat hanger) and disturb the mud and flush the best I could. I used rubber plugs as I knew the motor had to be hot tanked.
So it maybe mug at the bottom of the block.
Dave ----

Re: engine overheating

The delta across the radiator seems good. when i have measured it it might be 190 at the top and 130 at the bottom as i recall.

I doubt the engine has mud in it as it was rebuild (and i have receipt proof) at 100k. I would assume any crap would have been cleaned out then?

I'm a moonlight mechanic (is that a thing?) and don't know squat about timing, how to check it, or what that means - so if thats a likely issue id have to take it to my mechanic.

What surprises me is that you're saying ~210 is an ok operating temp?? Even for a trailer special? I'm not sure i like this because its only going to go higher under load. What is a dangerously high temp then??

The thermo issue seems likely, though - I've temped the ready cylinders /exhaust manifolds at continuously higher temps than the front. I was just thinking that was due to proximity to the upper rad hose. Also, what "bypass" is closed off by this thermo? (sry still learning about engines)

Re: engine overheating

While 210 might be a bit warmer than I'd expect, it should be at least the 195 of the 'stat. And thermostats aren't terribly precise. Nor are infrared thermometers. So 210 isn't hot by any means.

If your heater isn't kicking out heat then there are several possibilities:

1. Your heater core or a heater hose is plugged

2. Your heater controls aren't working correctly

3. Your fan isn't running to blow the hot air out

4. The engine really isn't warm, much less hot

As for the bypass, there's a link on the page previously reference to an ARE page that explains how it work.

But to boil it down (get the pun? ), most engines have one so that coolant is circulated through the block even when the thermostat is closed. Otherwise there would be hot spots in the engine that might cause damage. And, it would take a lot longer for the thermostat to "feel" the heat and open.

The vast majority of engines have an external hose for the bypass. But Ford designed the 335 Series, which includes the 351C, 351M, & 400, with an internal bypass. No hose to fail. But, it takes a special thermostat.

Re: engine overheating

While 210 might be a bit warmer than I'd expect, it should be at least the 195 of the 'stat. And thermostats aren't terribly precise. Nor are infrared thermometers. So 210 isn't hot by any means.

If your heater isn't kicking out heat then there are several possibilities:

1. Your heater core or a heater hose is plugged

2. Your heater controls aren't working correctly

3. Your fan isn't running to blow the hot air out

4. The engine really isn't warm, much less hot

As for the bypass, there's a link on the page previously reference to an ARE page that explains how it work.

But to boil it down (get the pun? ), most engines have one so that coolant is circulated through the block even when the thermostat is closed. Otherwise there would be hot spots in the engine that might cause damage. And, it would take a lot longer for the thermostat to "feel" the heat and open.

The vast majority of engines have an external hose for the bypass. But Ford designed the 335 Series, which includes the 351C, 351M, & 400, with an internal bypass. No hose to fail. But, it takes a special thermostat.

A bad water pump would also cause the motor to run hot.
If the impeller was slipping on the shaft the system would not flow what the factory built it to have.
This may even show up as no water flow thru the heater.

On the heater do both hoses get hot where you cant hold them?
On hoses does the lower radiator hose have the spring in side it?
If not then when at speed it will get sucked closed and stop water flow.
Dave ----

Re: engine overheating

Thanks for educating me on the bypass! sounds like a good idea as long as people install the right thermos. Ill probably end up purchasing a new and *try* to install it myself. God bless youtube lol. Not sure about the hoses but I've been looking for a good reason to put new rad hoses in, and my heater hoses look to have seen better days. I tried the ideas for burping my truck and added more coolant which seemed to help. I did notice that it seems to leak from the hose connection at the heater and then evaporates off, slowly dropping the coolant level. Ill also test my new thermo too as that seems to be highly recommended - thanks for all the help!

Re: engine overheating

Gary - my heater works fine i simply meant that it didn't do anything to reduce the engine temp per someones suggestion.

So it was blowing hot and it did not do any thing?
Most of the time it would lower it some and then start to go up again or take longer to "over heat".
I think you need to install a real temp gauge to see just what is going on and work from there.
Dave ----

Re: engine overheating

@Ray no ac in the truck unfortunately.

@Gary or others - just checking, if I buy Tim’s track boss thermostat for a Cleveland engine, am I correct in understanding that it will work in a 351m without the additional brass plate they mention as that’s “built in” to my engine? I couldn’t find any correlating part from Napa. These things are pricey!